1. Field of the Invention
The present invention relates to a method for manufacturing a part with one or more coils, and in particular to a method for fitting at least one ring coil into a corresponding channel formed in the inner circumference surface of a hollow cylindrical member such as a cylindrical core of a rotary transformer employed for a video tape recorder.
2. Description of the Prior Art
Video tape recorders are being improved for size-reduction and multifunction purposes. A rotary transformer, being one of the main components of a video tape recorder, has been improved and a cylindrical rotary transformer has been proposed in place of the conventional plate-type transformer.
The cylindrical rotary transformer requires a hollow cylindrical core having one or more ring coils at the inside surface thereof. The ring coils should be received in channels formed on the inner circumference surface of the cylindrical core so as to prevent the coils from protruding inwardly with respect to the inner surface thereof.
To form such a cylindrical core, lead wires are in advance attached to the coils which will in turn be fitted into the coil channels formed in the inside circumference surface of the core. In this case, each of the ring coils is formed to have a diameter substantially equal to the channel diameter, i.e., greater than the inner diameter of the core, and then inserted into each of the channels making the most of elastic characteristic of the ring coil.
Such coil fitting work is complex and difficult and takes a long time with manual operation, making it difficult to ensure a sufficient production and to improve yield because of damage to the coil during fitting. These disadvantages tend to frustrate use of the cylindrical rotary transformer in video tape recorders.